Applied Cryptanalysis Breaking Ciphers in the Real World pdf

Applied Cryptanalysis Breaking Ciphers in the Real World Wonderful Digest

1.1 Introduction

Most of this chapter is devoted to introducing terminology and discussing a select few classic “pen and paper” ciphers. Our goal here is not to cover clas-sical cryptography in detail, since there are already many excellent sources of information on such ciphers. For example, Kahn’s history [74] has a general discussion of virtually every cipher developed prior to its original publica-tion date of 1967, Barr [7] presents a readable introduction to cryptography,Spillman [139] nicely covers the cryptanalysis of several classic cipher systems and Bauer [8] provides rigorous coverage of a large number of classical crypto topics. The ciphers we discuss in this chapter have been selected to illustrate a few important points that arise in upcoming chapters.

Even if you are familiar with classical cryptosystems, you should read the next two sections where terminology is discussed, since the terminology in cryptography is not always consistent. In addition, the material in Sec-tions 1.4.3 and 1.4.4 is directly referenced in upcoming chapters.

1.2 Good Guys and Bad Guys

In cryptography, it is traditional that Alice and Bob are the good guys who are trying to communicate securely over an insecure channel. We employ Trudy (the “intruder”) as our generic bad guy. Some books have a whole cast of bad guys with the name indicating the particular evil activity (Eve,the eavesdropper, for example), but we use Trudy as our all-purpose bad“guy”.